The Bush administration assured the Supreme Court last December that Guantanamo Bay prisoners who felt they were unfairly being detained could have their cases thoroughly reviewed by a federal appeals court. Now, it's not so clear.

When the first case arrived at the appeals court, the Justice Department told the judges they could look at the evidence but should act on the assumption that the military made the right decisions at Guantanamo Bay.

That assertion led to a testy exchange recently between Appellate Judge Merrick B. Garland and Justice Department attorney Gregory Katsas. Garland wanted an explanation for the contradiction. Katsas said there was no contradiction at all.

The exchange underscores the challenge facing the administration: It doesn't want judges overseeing terrorism cases, but it can't eliminate them from the process without first getting their approval.

Normally, a prisoner who believes he's being unfairly detained can ask the courts to free him. It's a right known as habeas corpus that dates back to the 1300s and was written into the Constitution.

But the administration says that right does not exist for Guantanamo detainees. For years, administration officials have tried to limit judges' role in hearing detainees' cases and twice the administration has been set back by the Supreme Court.

Currently, prisoners labeled enemy combatants can only challenge that finding in the U.S. Court of Appeals for the District of Columbia Circuit. The Supreme Court is considering whether that violates the principles of habeas corpus. A decision is expected by the end of June.

During arguments in December, Justice John Paul Stevens was particularly interested in what role the government envisioned for the appeals court. Was the court supposed to defer to the military? Or should the court conduct what's known as a preponderance review, by balancing all the evidence and deciding whether the detainees really are enemy combatants?

Solicitor General Paul Clement was clear about what detainees could expect: "They're specifically entitled to a preponderance review in the D.C. Circuit," he told Stevens.

Stevens asked again. Clement again said the law called for a full review.

The outcome of the case means a great deal to detainees, who want an independent government branch to thoroughly review the military's decisions.

But before the high court could rule, detainee Huzaifa Parhat brought his case to the appeals court. Parhat never fought against the U.S. and the government concedes there's no evidence he ever intended to. He has been held for six years because he is linked to a Chinese separatist group that the military says has some ties to the al-Qaida terrorist network.

Is that enough to warrant indefinite imprisonment? Under the standard that Clement laid out in December, Parhat's lawyers say no. But Katsas, the deputy assistant attorney general, called for a different standard. He said the court should be "deferential" to the military's decision and only overturn it if the evidence it is clearly unreasonable.

Judge Garland sounded perplexed.

"That is not what the solicitor general of the United States said to the Supreme Court," Garland said.

He read Clement's comments to Katsas.

"So you are saying he misspoke? The question couldn't have been clearer to him. Are you saying, I mean, this was presented, and it was presented in this way because it was a very important issue to the court," Garland said. "Do you want to change the government's position, either by filing a letter with the Supreme Court or by filing a letter with us?"

Katsas said there was no contradiction. He said detainees were entitled to a full review of the evidence, but it's up to the military to conduct that review. The appeals court can reconsider the military's decision, but it must presume the decision was correct.

That's consistent with the position Clement took in Supreme Court briefs last October, when he said courts had to be deferential to the decisions made at Guantanamo Bay. Months later, he seemed to tell the justices that the appeals courts could conduct a preponderance review, which Katsas now says they cannot.

The Supreme Court is expected to rule soon on the new detainee law. In doing so, it might spell out what role the appeals court is supposed to play.

It may sound like a mere argument about words - a semantics debate between "preponderance" and "deferential" - but the outcome will help determine how much oversight courts have over what happens at Guantanamo Bay.